In Emacs 31, we can now detect cloned and undeleted frames during make-frame

[shipmints]

This can enable a call to bufferlo-clear in an after-make-frame-functions hook to allow a frame to start fresh without whatever buffer happened to be current when the frame was made. We would exempt cloned and undeleted frames from this treatment. We could make this the default behavior, which I think most people probably expect since buffers are supposed to be marked local only when actually used, or make it optional.